The One Who Knows Everything Elimination Thread
Since I was correct that they were going to Konoha, I think it's safe to say that we can eliminate these characters as the one who knows everything:
1 Konoha Elders: Sasuke and co. did not enter Konoha itself but rather its surrounding vicinity, but the two elders are always inside buildings or the Hokage quarters, and there would be no need to revive Oro if Sasuke just wanted to meet those two.
2 Uchiha Stone Tablet: Sasuke already knows where it is, why the need to revive Oro just to go there? Plus it was clearly mentioned that they were meeting someone, not something. The tablet is a thing.
3 Sasuke's parents/ Uchiha clan : I doubt their burial place was kept secret, since in the eyes of the villagers they weren't traitors for no one knew that they were planning a coup except for the third hokage, danzo and the two elders so they were most probably buried in the cemetery where all Konoha shinobi are interred like Asuma.
4. The Death Reaper/hokages: it is clearly shown that they were going to a specific place within the vicinity of Konoha, the reaper is not located in any specific place for it is summoned by using RDS and not by searching for it in a specified location.
5. Sons of the Sage: they existed before konoha was founded, why would they be located/ lived in a place founded centuries after they died? and also adding doubt that they were the ones they are seeking is the fact that since they were powerful individuals, why didn't Oro resurrect them long ago and used them to conquer the world?
My prime suspicion is that it is Shisui Uchiha's body that they are seeking and Oro will use the scroll to Edo Tensei him, since Shisui's body was missing, I suspect Danzo took his body for safe keeping or for experimentation purposes but did not want Oro to acquire it, Oro and Danzo were in connivance before so Oro probably knew where Shisui's body was but Danzo kept it safe guarded from him. Sasuke having acquired Itachi's memory of the events must have also been made aware of Shisui's corpse hidden by Danzo, Itachi probably knew or suspected Danzo's hand in the disappearance of Shisui's corpse but didn't try to recover it because of his secret pact with Konoha to kill his clan and work as an undercover spy within Akatsuki, for if he tried to steal the body he would have acted in betrayal against the leaf and Danzo who was a leader of it. That would've also jeopardized Sasuke's safety when he was still living in the village.
PS: I'm sorry If I accidentally double posted my thread, I'm using my Ipad so I clicked the wrong buttons, so sorry.